Hello, like it says in the title, the pedals go round freely but it wont engage anything!! I've read posts on here about the free wheel and free hub, its not that, that works like it should, literally the only thing that is going wrong is the pedal arms, just spinning on the spot, not even turning the big chain sprocket. Is there anything I can do to fix this???

To answer this is there any way you could give more information or possibly upload a picture? What type of crank is it, like is there more then one "big chain sprocket"? That is in the front right, where the problem exists?

Good maintenance to your Bike, can make it like the wheels are, true and smooth!